1. Field of the Invention:
The present invention relates to medical catheters and more particularly to catheters that are maneuverable through anatomical cavities, vessels, and other structures of the body.
2. Discussion of Background:
Generally, the term "catheter" encompasses a wide array of devices for accessing remote locations, particularly within interior bodily vessels and cavities. Medical catheters may be used for tissue sampling, temperature measurements, drug administration, or electrical stimulation to a selected tissue. With fiber optics, they may carry light for visual inspection of tissues. Catheters may also be used in industrial environments to inspect the otherwise inaccessible interiors of equipment.
One serious drawback in using catheters is maneuvering them in the desired direction. Catheters are pushed, rather than pulled, and therefore tend to move in a straight line unless they are warped or meet with resistance, in which case they move in a less resistive direction. If the path is relatively straight and nondiverging, maneuvering is less of a problem. However, in blood vessels, for example, maneuvering into the correct branch of an artery can be quite difficult. A catheter might be inserted into a femoral artery and advanced along the arterial system through numerous branches in order to arrive in a coronary artery. The catheter must be advanced carefully through paths that are not straight but do have bends and turns so as not to damage tissue. It is highly desirable to be able to steer the catheter to avoid tissue damage and to be able to select one path when more than one present themselves. Several techniques have been developed to maneuver a catheter.
Catheters with heat-activated "mechanical memory" elements are known. The temperature-activated element has a first memory shape and a second straightened shape. The catheter is placed in the pathway in the straightened shape and when electrically heated to a predetermined temperature, the element will undergo bending to the memory shape, thereby effecting the desired change in direction of the tip of the catheter. An example of such a device is found in U.S. Pat. No. 4,543,090.
Catheters with contracting members that undergo axial shortening when an electrical current is applied are also known. An example of this type catheter is set forth in U.S. Pat. No. 4,934,340. Other means of bending catheters utilize fluids or permanent magnets and magnetic fields.
Although such devices incorporate means for bending the tip of a catheter, they are less than optimal for certain medical procedures because they are difficult to control and manipulate and they are relatively bulky. Accordingly, there remains a need for a small, steerable, maneuverable catheter.